Pity the second-generation Chevrolet Camaro. Born late — a delivery fraught with complications — it was nearly snuffed out in adolescence. Although it survived to a ripe old age, the second-gen Camaro has never inspired the same nostalgia as its beloved 1967-1969 predecessor, perhaps because it arrived in the fray of one of the most contentious public debates of the 20th century: the battle over automotive emissions and the use of lead as a gasoline additive. This is the story of the 1970-1981 Chevrolet Camaro and the rise and fall of leaded gasoline.

THE SECOND GENERATION CHEVROLET CAMARO

The first-generation Chevrolet Camaro, Chevrolet’s belated response to the Ford Mustang, bowed in the fall of 1966 as a 1967 model. Although it won respect for its performance and muscular appearance, neither the Camaro’s looks nor its muscle were enough to let it seriously challenge the popularity of the Mustang. Dearborn’s “pony car” regularly outsold the Camaro (and its F-body sister, the Pontiac Firebird) by a considerable margin. Before its first model year was over, however, Hank Haga’s Chevrolet Styling Studio 2 was already at work on the second-generation Camaro.

The new Camaro was planned for the 1970 model year, which would ordinarily have put it on sale in the fall of 1969. As it happened, the new car didn’t appear until February 26, 1970, around five months late. There is a popular assumption that the delay was caused by labor issues — GM clashed repeatedly with the United Auto Workers union (UAW) between 1969 and 1972 and there were several lengthy strikes during this period. However, the Camaro Research Group says the real reason for the delay was a serious problem with the new car’s complex rear quarter panel dies, which forced Fisher Body first to modify and then to completely redesign the affected tooling. That in turn forced GM to keep the 1969 Camaro in production for an extra four months.

These 1970 Chevrolet Camaros (both ’70 1/2 models) have the popular Rally Sport option, which added driving lights inboard of the headlamps and removed the center grille bar and overriders, substituting a more protruding plastic nose clip with small “bumperettes” on either side of it.

When the second-generation Chevrolet Camaro finally did appear, it made a tremendous splash. It was one of the most radical-looking new designs the industry had seen since the excesses of 1959.

Unlike the Mustang, whose successive revamps from 1964 to 1973 represented a steady evolution of the original concept, the new Camaro was an almost complete stylistic break with its predecessor. The first Camaro, as we have previously seen, evolved from the “Super Nova” concept car of the early sixties and essentially married the stylistic philosophy of the second-generation Chevrolet Corvair (1965-1969) with the short-deck, long-hood proportions popularized by the Mustang; park a 1967 Chevrolet Camaro next to a post-1965 Corvair and the family resemblance of their basic body shapes is readily apparent. In contrast, new Camaro looked more like something from Italy than Detroit. It featured a curvaceous nose and gaping grille that recalled early-sixties Ferrari or Maserati GT cars — particularly on Rally Sport models, which had no bumper ahead of their grille openings.

This is a 1973 Chevrolet Camaro, which has a reinforced front bumper (not immediately obvious) to meet federal requirements for 5 mph (8 km/h) crash protection. If this were a real 1973 Z/28, it would have the 245 (net) horsepower (183-kW) L-82 engine; in any case, this car has Turbo Hydra-Matic automatic transmission.

Under the skin, the new F-body was much more familiar. It was about 2 inches (51 mm) longer, slightly wider, and somewhat lower than the 1969 Camaro, but was structurally very similar. It retained the first-generation car’s semi-monocoque construction, with a separate front subframe carrying the engine and front suspension, and suspension design and powertrain choices were substantially the same as before. Front disc brakes were newly standard, but the four-wheel discs that had been available on a very limited basis in 1969 were gone. The new Camaro was almost 200 pounds (90 kg) heavier than the old, thanks to the addition of new side-guard door beams as well as the more complex inner body stampings necessary to accommodate its curvy shape.

The high-performance Z/28 option package returned for 1970, but Chevrolet abandoned the earlier Z/28’s high-strung 302 cu. in. (4,942 cc) engine in favor of the new 350 cu. in. (5,733 cc) LT-1. The LT-1, shared with the Corvette, was rated at 360 gross horsepower (268 kW) — about as a strong as the underrated 302, but far more tractable. An additional advantage was that the Z/28 could now be ordered with automatic transmission, whereas first-gen Z/28s had required a four-speed manual. A big-block V-8 remained optional on other Camaros. Chevrolet still called the big Turbojet V-8 a “396,” but it was now actually 402 cubic inches (6,587 cc), rated at 350 gross horsepower (261 kW). Chevrolet briefly announced that the Camaro would offer the big 454 cu. in. (7,443 cc) LS-6 engine offered in the 1970 Chevelle SS, rated at a whopping 450 gross horsepower (336 kW), but the option was dropped before it went into production.

Like the first-generation Chevrolet Camaro (and the Mustang), the second-generation Camaro had exaggerated long-hood, short-deck proportions, which gave it a muscular look. Note the flared front wheel wells: The second-generation Camaro’s front tread width was 1.6 inches (41 mm) wider than before, although overall width was only 0.4 inches (10 mm) greater. With fat F60-15 tires, standard on Z/28s, the Camaro handled well by the standards of its era, although its grip can be matched by many modern family cars. Its brakes were also marginal for the car’s weight, fading prodigiously in hard use.

The 1970 Chevrolet Camaro was just about as fast as its predecessor despite its extra weight. Car and Driver put its well-prepared automatic Z/28 across the quarter-mile line (402 meters) in the low 14-second range with a trap speed of slightly over 100 mph (161 km/h); Motorcade‘s Dave Epperson managed similar figures. That was excellent performance, but the bottom was about to fall out.

GETTING THE LEAD OUT

About nine months after the Camaro’s belated debut, the U.S. Congress unanimously passed the Clean Air Act of 1970, empowering the recently created Environmental Protection Agency (EPA) to set and enforce standards for air pollution. The federal government had begun setting limits on automotive emissions for the 1968 model year, two years after the state of California initiated its own, more-stringent standards, but the Clean Air Act called for a 90% reduction in automotive emissions by 1975. It also reopened a very old can of worms: the use of lead in gasoline.

To understand the history of leaded gasoline, we must examine some of the basic engineering concepts involved. A four-stroke engine, like that used in most automobiles, compresses its air-fuel mixture before burning it. One of the most effective ways to improve both an engine’s specific output (its power per unit of displacement) and its specific fuel consumption (fuel burned per unit of power produced) is to increase the static compression ratio (the ratio of the swept volume of each cylinder and combustion chamber when the piston is at bottom dead center — its lowest point — to the combustion chamber volume when the piston is at top dead center — its highest point).

This has two effects: First, it increases the density of the mixture, packing oxygen and fuel molecules more tightly together, which allows more complete combustion. Second, it increases the energy of that mixture through adiabatic heating, allowing more energy to be extracted from the mixture when it burns. As a result, a higher compression ratio improves both power and fuel economy, which is why the auto industry — spearheaded by General Motors — has long been enthusiastic about high-compression engines like the Camaro’s high-revving LT-1.

Like the first-generation F-body, the second-generation Chevrolet Camaro was a monocoque aft of the cowl, with a rubber-isolated subframe carrying the engine, front suspension, and forward sheet metal. At 188 inches overall, it’s about 2 inches (50 mm) longer than the ’69 and 3.4 inches (86 mm) longer than the ’67-’68.

A major drawback of raising a gasoline engine’s compression ratio is that increasing the temperature of the mixture by compressing it increases the chances that the mixture will ignite either before or after the spark plugs fire. This is called autoignition, also known as detonation, pinking, or engine knock. Because knock is uncontrolled detonation, typically occurring around hot spots in the combustion chamber, it has the potential to cause severe engine damage. Finding ways to raise the compression ratio of gasoline engines without causing catastrophic knock was a daunting challenge for early automakers and engine manufacturers.

PUTTING THE LEAD IN LEADFOOT

One of the engineers pursuing that goal was Charles F. Kettering, the founder of Delco (later a GM division) and, after selling Delco in 1916, the Dayton Metal Products Corporation (DMPC). Kettering was a brilliant and prolific engineer involved in many major automotive innovations, notably the development of the first electric starter motor, adopted by Cadillac in 1912.

Not long after that, Kettering became interested in finding ways to control engine knock to allow higher compression ratios. It was already understood that the use of different fuels affected a given engine’s susceptibility to knock. Ethyl alcohol, for example, was already known to provide greater knock resistance than gasoline, although the reasons were not yet well understood. Kettering and his assistant, engineer Thomas Midgley, Jr., who had worked with Kettering at Delco and joined him at DMPC, hypothesized (correctly) that the knock resistance of a given fuel depended on the fuel’s ability to absorb heat without igniting. From that, they concluded that it would be possible to increase a fuel’s resistance to detonation by altering its formulation or using additives.

In 1917, Kettering and Midgley developed an antiknock fuel using a mixture of cyclohexane and benzene, which they successfully demonstrated to the U.S. Army Air Corps. In 1918, DMPC filed a patent on this use of benzene, intending to manufacture it, but the end of the war and the withdrawal of Army interest put the project on the shelf.

A year later, Kettering sold DMPC to General Motors and became head of GM’s research subsidiary, again bringing Midgley with him. GM was very interested in the idea of antiknock fuel additives, which had obvious commercial potential — particularly considering that more than a third of GM stock was then owned by the oil company E. I. du Pont de Nemours and GM and du Pont shared several board members.

The Chevrolet Camaro’s Z/28 package was an option package, not a model, costing $598.05 in 1973 (down from $766 the year before). In 1973 the package included the L-82 engine, sport suspension, 15-inch wheels, dual outside mirrors, and a black-painted grille. The twin stripes, commonly associated with the Z/28 since 1967, were actually an additional option, RPO D88, costing $77. The Z/28 package was discontinued after 1974 and did not return until 1977.

Interestingly, the initial impetus for increasing the compression ratios of automotive engines was not the quest for more power, but rather the need for greater fuel economy. While we tend to think of oil shortages as a modern preoccupation, there was considerable anxiety even before 1920 that U.S. oil consumption would soon outpace domestic reserves, eventually forcing the U.S. to buy much of its oil overseas. Kettering believed that wider use of more efficient engines would help to forestall that eventuality until alternatives to fossil fuels became available.

At the time, Kettering believed that oil’s principal successor would probably be ethanol. Midgley demonstrated that a 70/30 blend of gasoline and ethanol provided excellent knock resistance, allowing what were for the time exceptionally high compression ratios. However, Kettering recognized that producing ethanol in large quantities for fuel use would require the development of means to produce alcohol from cellulose farm waste rather than food crops — something that was becoming feasible, but not yet economically viable. In the interim, Kettering and Midgley sought a “low percentage” antiknock additive for gasoline, a goal that dovetailed with their employer’s commercial ambitions.

In late 1921, after years of extensive trial and error that by some accounts involved thousands of experiments, Midgley finally hit upon an effective answer: lead tetraethide, more commonly called tetraethyl lead (TEL). Although TEL was not easy to produce and making it a workable fuel additive took further development, even small quantities could significantly increase gasoline’s heat absorption capacity, which greatly improved knock resistance.

General Motors first demonstrated the use of TEL as an antiknock additive in the summer of 1922. By late 1923, du Pont had developed several patented means of manufacturing TEL, which allowed commercial sales to commence. In mid-1924, GM and Standard Oil of New Jersey (the predecessor of the modern Exxon-Mobil Corporation) formed the jointly owned Ethyl Corporation to sell TEL under the trade name “Ethyl.” The name was suggested by Kettering, who became the new company’s first president.

Despite early public controversy about the use of TEL, Ethyl was very successful. It was all but universal in American gasoline by the late thirties and began to proliferate overseas even before the war. High-octane leaded aviation gasoline fueled many of the military aircraft engines of World War II. By the mid-fifties, there was also high-octane premium pump gasoline, supporting the emergence of a new generation of powerful OHV V-8s.

(As a side note, in 1926, Ethyl scientists developed the octane scale (based in part on an idea of Midgley’s) for quantifying the knock resistance of a given fuel. The scale was based on the properties of two of the hydrocarbons commonly contained in gasoline: heptane (n-Heptane) and iso-octane (2,2,4-Trimethylpentane). Since heptane’s knock resistance was poor, it became the zero point of the scale while pure iso-octane was assigned a value of 100. A fuel’s octane number was its knock resistance relative to a blend of heptane and iso-octane; for example, a fuel with knock resistance equivalent to a 50/50 blend of the two hydrocarbons would have an octane number of 50 while a fuel comparable to a 95/5 blend of iso-octane and heptane would have an octane number of 95. Some fuels, such as pure ethanol, actually have octane numbers lower than pure heptane or higher than pure iso-octane, providing octane numbers less than 0 or more than 100. There are now several different octane rating systems using different methods to calculate a given fuel’s knock resistance.)

THE LEADED GASOLINE CONTROVERSY

Aside from the manufacturing and engineering challenges it presented, the principal drawback of TEL as a fuel additive was that lead is a deadly neurotoxin. Before World War II, lead was still widely used in a variety of consumer products like paint and glassware, but its toxicity — whether consumed or absorbed through the skin — was well known.

Public health advocates like Yandell Henderson of Yale University and Alice Hamilton of Harvard Medical School, who had written about the dangers of lead poisoning for more than 15 years, were unhappy about the use of TEL in motor fuel almost from the start. Their concern was not theoretical: Some members of Kettering’s own staff, including Midgley, suffered the effects of lead exposure and more than a dozen du Pont and Standard Oil workers died of lead poisoning between 1923 and 1925. The state of New Jersey actually filed criminal charges against Standard Oil in connection with the deaths of workers at a plant there, but a grand jury did not bring an indictment.

In 1925, Ethyl temporarily suspended production while the U.S. Public Health Service held public hearings on TEL. At those hearings, representatives of GM, Standard Oil, and Ethyl claimed there were no viable alternatives to TEL and dismissed the public outcry as unwarranted alarmism. The surgeon general appointed an investigatory committee, whose report, issued in January 1926, concluded that there were insufficient grounds to ban the use of TEL in gasoline, although the committee acknowledged that the data was very limited and strongly recommended further research. The PHS didn’t follow up on that recommendation, but in 1927, the surgeon general specified a voluntary limit of 3 cc of lead per gallon (raised in the late fifties to 4 cc per gallon, equivalent to about 4.23 grams per gallon or 1.12 grams per liter).

The controversy soon faded from the public consciousness in the U.S., although similar questions were raised when TEL was adopted in the U.K. By the mid-thirties, the safety of Ethyl was taken sufficiently for granted that in 1936, the Federal Trade Commission ordered an Ethyl competitor, Cushing Gasoline and Refining Company, to desist from charactering Ethyl’s product as dangerous or unhealthy.

After the war, an emerging body of scientific research linked high blood lead levels due to environmental lead contamination (including the burning of leaded gasoline) to a sobering array of health problems, particularly among children. (Today, the Centers for Disease Control consider blood lead levels of more than 5 micrograms per deciliter grounds for public health action.) Some of the binding chemicals used with TEL, such as ethylene dibromide (EDB), were later identified as health hazards as well; the EPA now warns that exposure to EDB (usually through the consumption of contaminated water) can contribute to liver, stomach, and kidney problems and an elevated risk of cancer. Nonetheless, the oil and auto industries continued to deny that the use of leaded gasoline posed any substantive public health risks.

In the sixties, leaded gasoline became one of the targets of an emerging U.S. movement to improve automotive safety and reduce harmful emissions. In 1969, U.S. Secretary of Health, Education, and Welfare Robert Finch proposed that major oil companies begin phasing out leaded gasoline starting in mid-1971.

THE MOVE TO UNLEADED GASOLINE

Surprisingly, the first U.S. automaker to support the push for lead-free gasoline was General Motors, whose president, Ed Cole, announced in January 1970 that GM could reduce the compression ratios of all its engines to make them compatible with unleaded gasoline starting with the 1971 model year. General Motors and Standard Oil had divested themselves of the Ethyl Corporation in 1962, but Cole’s announcement nonetheless startled many in the auto industry.

Around the same time, Henry Ford II, chairman of Ford Motor Company, sent a letter to 19 major petroleum producers asking them to begin offering lead-free fuels. Leaded gasoline, whose use had been taken almost completely for granted even five years earlier, was suddenly on its way out.

Although some U.S. health officials now characterized lead as a public menace, the auto industry was careful to attribute the transition to unleaded gasoline not to any inherent health risk of leaded fuels, but to the need to prepare for the adoption of catalytic converters for emissions control. Leaded gasoline is incompatible with catalytic converters because lead deposits quickly foul the catalyst; lead has a similar effect on oxygen sensors, later adopted for electronic engine management systems.

The second-generation Chevrolet Camaro’s broad sail panels, with no rear quarter windows, did nothing for rear visibility. Unlike the first-generation car, the second-generation Camaro was never offered as a convertible. This car appears to be a 1973 Camaro, but it has the raised Z/28 emblem of a 1971 or 1972 car (replaced by a foil decal on the ’73s) and the chrome exhaust tips of a ’71 (dropped in ’72). The spoiler is from a post-1974 car; although spoilers were optional as RPO D80, the 1973 spoiler didn’t wrap around the fenders. This car is also missing the corresponding front spoiler that was included with RPO D80.

In late 1973, the EPA announced the beginning of a mandatory phaseout of leaded gasoline. A lawsuit by du Pont and the Ethyl Corporation temporarily blocked that mandate, but in 1976, a federal court of appeals upheld the phaseout regulation; the U.S. Supreme Court declined to hear the case.

Editorials in the automotive press mostly condemned the transition to low-lead and lead-free gasoline. Many of the editors were already deeply critical of safety and emissions regulations, seeing them not as public health actions, but as overweening ‘nannyism’ by politicians and car-hating zealots with no engineering knowledge. The lowering of compression ratios to allow more emissions-control devices was seen as just another blow to the editors’ beloved sports cars and Supercars. (Ironically, the widespread adoption of catalytic converters and electronic engine controls — which, at least in the U.S. and Japan, were adopted primarily for emissions reasons — would later allow a performance renaissance, but that didn’t happen for more than a decade and would have seemed entirely improbable in the early seventies.)

THE FALL AND RISE OF THE CAMARO

General Motors kept its promise of lower compression ratios: For the 1971 model year, even the high-winding Chevrolet LT-1’s compression ratio dropped from 11.0:1 to 9.0:1.

In the Camaro, the effects were immediately apparent. Comparing their 1971 Camaro Z/28 to the 1970 model, Car and Driver found that the low-compression engine reduced quarter-mile trap speeds — a reliable measure of a car’s power-to-weight ratio — by almost 7 mph (11 km/h) even though the 1971 test car was almost 100 pounds (45 kg) lighter than the 1970 car. Although Chevrolet claimed that the reduced compression ratio cost the LT-1 engine only about 15 net horsepower (11 kW), the magazine’s editors estimated that the drop was more than 40 hp (30 kW).

The decline for 1971 was only the beginning. For 1972, the LT-1’s net horsepower fell to 255 hp (190 kW). The best quarter-mile time Road & Track‘s 1972 Z/28 automatic could manage was the mid-15-second range, with trap speeds of about 90 mph (145 km/h). For 1973, the LT-1 was replaced by the L-82, which had a milder camshaft with hydraulic rather than mechanical lifters. Rated at 245 net horsepower (183 kW), the L-82 was now the Camaro’s most powerful engine — the 402 had been dropped after the previous season. The milder engine had to move a heavier car; new 5 mph (8 km/h) bumper standards further inflated the F-body’s already substantial curb weight.

This 1973 Chevrolet Camaro has the steering wheel of the new Type LT, a luxury-oriented model introduced for 1973, but is not a Type LT — it doesn’t have the LT’s woodgrain dashboard trim, de-chromed exterior trim, or concealed windshield wipers. It does have the optional full instrumentation, standard with Type LTs and an $82 option (RPO U14) without it. You could order the Z/28 package with the Type LT, which cost $389 more than a standard V-8 Camaro Sport Coupe and accounted for about a third of total Camaro sales that year.

The Camaro’s ever-increasing weight and worsening power deficit were moot points for many buyers, who were now hit with prohibitive insurance surcharges on all but the mildest pony cars. Sales of all sporty cars were shrinking and the second-generation Camaro’s sales were further impacted by a lengthy work stoppage at the Camaro plant in Norwood, Ohio, that cut total production for the 1972 model year by around 40,000 units. More than 1,000 completed cars then had to be scrapped because they were finished too late to be legally sold as 1972 models; they didn’t meet the tougher federal safety and emissions standards that took effect for the 1973 model year.

Federal safety standards led to the adoption of new, much more prominent bumpers on 1974 Chevrolet Camaros like this one, increasing overall length by about 7 inches (177 mm) over the ’73 model. The nose clip behind it was now fiberglass. The mass of the bumpers and their shock absorbers added more than 200 pounds (90 kg) to the Camaro’s curb weight, cutting further into its performance and gas mileage.

Facing those problems, GM seriously considered dropping both the Camaro and its F-body sibling, the Pontiac Firebird. Other automakers were also cutting their losses; the Dodge Challenger, Plymouth Barracuda, and AMC Javelin would all expire in 1974 while Ford reinvented the Mustang as the Pinto-based Mustang II.

Thanks in part to a grassroots campaign both inside and outside GM, Chevrolet and Pontiac finally decided to stay the course. For 1974, the Camaro and Firebird received a facelift that neatly incorporated the new 5 mph bumpers. The revised styling inevitably lacked the purity of the earlier second-gen cars, but met the new federal requirements while preserving the F-bodies’ sporty image.

Although performance continued to erode due to greater weight and more stringent emissions standards, Camaro sales picked up nicely, no doubt helped by the greatly diminished competition. Both the Camaro and the Firebird remained popular and profitable enough to last through the 1981 model year.In 1974, the Chevrolet Camaro got a facelift that included recessed “sugar scoop” headlamps. The Type LT, starting at $3,380.70, accounted for about 49,000 sales, almost a third of the 151,000-odd Camaros sold for 1974.

LEAD REQUIEM

The demise of leaded gasoline proved to be a protracted struggle. The Reagan administration attempt to roll back the lead phaseout in 1981, but political pressure forced them to relent the following year. Most U.S. automotive gasoline was lead-free by 1986, although the use of leaded fuel for on-road vehicles was not completely banned until the end of 1995. NASCAR didn’t adopt unleaded racing fuel until early 2007.

The 1974 Chevrolet Camaro had a number of one-year-only features: It was the only big-bumper Camaro to retain the original rear window, which was replaced with a wrap-around design the following year in an effort to improve rear visibility. Note the concealed windshield wipers, which sit behind the trailing edge of the hood — this was a standard Type LT feature.

Ethyl and its rivals continued to aggressively market TEL outside the U.S. through the nineties. Japan had phased out leaded fuel in the mid-seventies, again prompted mostly by the planned adoption of catalytic converters, but unleaded fuel did not become widely available in Europe and the U.K. until the late eighties and the European Union didn’t ban leaded gasoline for passenger car use until 2000.

Leaded petrol remained common in other nations, such as India, into the new century, but its use has rapidly declined over the past decade. In 2011, the UNEP Partnership for Clean Fuels and Vehicles estimated that only about a half a dozen countries still use leaded gasoline for motor vehicles. TEL is still used in aviation gasoline, although most modern avgas is 100-octane “low lead” rather than the earlier 130-octane “highly leaded” variety.

The transition to unleaded gasoline has been costly and some non-TEL octane boosters may be hazardous in their own right. While the EPA Office of Water says there’s not enough data to determine whether exposure to low levels of MTBE (methyl tertiary butyl ether) is a health hazard, the agency warns that higher levels of the additive may be carcinogenic. The good news is that the EPA estimates that Americans’ average blood lead levels dropped 78% between 1978 and 1986; a 2007 Amherst College study linked reduced blood lead levels to concurrent decreases in the incidence of violent crime. Still, lead doesn’t break down or decay, so the impact of past use of leaded gasoline may never entirely disappear.

Although this is definitely a 1974 Chevrolet Camaro, the hood and its prominent hood scoop are taken from a 1980 or 1981 car. It was theoretically functional: A solenoid opened the trap door at the rear of the scoop to admit cool outside air to the engine. Since this car is probably not a real Z/28, it presumably has one of the other 350 cu. in. (5,733 cc) V-8s. If this was originally a California car, that probably means the LM-1, a $46 option providing 160 net horsepower (119 kW) and 270 lb-ft (365 N-m) of torque.

What about the poor, beleaguered second-generation Camaro? Ironically, its popularity at the time has done no favors for its reputation today. Although the Camaro was never very common outside the U.S., if you’re an American of a certain age, the chances are that you either owned one or knew someone who did. Sheer ubiquity soon dulled the impact of styling that seemed so fresh and daring in the spring of 1970. By the time its replacement bowed in the fall of 1981, many people were more than ready to forget it and the era of stylistic excess, inflation, gas rationing, and controversy in which it appeared.

The early (1970-1972) second-gen cars have a strong fan base, but they’ve never been as desirable as the first-generation Camaro and probably never will be. That’s a shame — had the Camaro appeared before the smog and safety controversies, it would probably be considered a classic like its predecessor.

Sometimes, history has no mercy for those born in the wrong place at the wrong time.

14 Comments

As compression ratios of engines increased, so did gasoline octanes. In the mid-1950s, premium gasolines had octane ratings of 96 and jumped to 98 by 1957-58 as compression ratios hit the 10 to 1 level and higher. Some oil companies introduced “superpremium” grades of 102 octane including Golden Esso Extra (in a gold pump 1956-61), Gulf Crest (the juice in the purple pump, 1957-61), and Chevron Custom Supreme (in the white pump, 1959-70) and of course, Sunoco 260 – which was the top of their 8-grade Custom Blended line.
Most oil companies stuck with only two grades of gasoline (regular and premium) and competed with the superpremiums by increasing their “premium” gasoline octanes to 99-100 octane including Super Shell, Texaco Sky Chief, Phillips 66 Flite Fuel, Mobil Premium, Royal 76, Sinclair Dino Supreme, DX Super Boron, etc.

Esso and Gulf discontinued their superpremiums in late 1961 due to low sales and simply increased the octanes of their premium gasolines Esso Extra and Gulf No-nox to within 1 or 2 octanes of Golden and Crest, with Esso replacing Golden with a mid-grade Esso Plus and Gulf repainting the purple pumps blue for its new subregular Gulftane.

Then there were additives and promos of these high-octane premiums including Shell’s TCP and Platformate, Texaco’s Sky Chief with Petrox that Jack Benny was persuaded to put in his Maxwell to save him money (I’ll try a gallon), and Nickel Compound in Sinclair Dino Supreme, along with Esso’s “Put A Tiger in Your Tank” and Mobil’s “Detergent Gasoline” that cleaned carburetors, PCVs and whole fuel systems.

Gulf stations during 1966-67 gave away free orange “Extra Kick Horseshoes” to motorists who purchased “No-nox” gasoline that were placed on the bumpers of cars. Esso (Enco in the central and west) stations gave away free tiger tails that were tied to gas tank fillers.

And regular gasoline was not exactly “wimpy” in octane, either, as the cheaper fuels rose in octanes from about 91 from 1956-58 to 94 by 1965-66.

It’s worth noting — as you’re probably already aware (but some other readers may not be) — the octane numbers are all research octane numbers, and as such don’t correspond directly with the pump octane ratings found on modern U.S. gas pumps. Pump octane is an average of the research octane number and the motor octane figure, so if sold from a modern pump, 94 RON gasoline would be rated less than 94 octane.

Also, while different manufacturers have promoted it to different degrees over the years, all modern gasoline (and motor oil) does contain detergent. They don’t necessarily used the same detergents, or the same amounts, but it has been universal for some years.

That is correct about the change in gasoline octane measurements from “Research” in the 1960s to today’s “Pump” octane is somewhat similar to the changes in engine horsepower measurements from the “gross” figures of 1971 and earlier on a dynometer without mufflers, accessories and emission equipment, to the “net” ratings of 1972 and later that were based on an engine as “installed” in a vehicle with exhaust system, accessories and emission controls installed.

Today’s 87 “Pump” octane unleaded regular is the same fuel as the 91 “Research” octane fuel that was recommended in the 1971 Camaro owner’s manual. Similar spreads of 4-5 octane differences in fuels between pump and research exist for mid-grade unleaded – 89 Pump octane or 93 Research octane (just slightly below the 94 research octane for regular-grade fuel in 1971) and 93 Pump octane unleaded premium would be 97-98 research octane, or just slightly below the 99-100 research octane of leaded premium in that era.

Another fact to consider. While almost all oil companies went to lead to increase gasoline octane in the 1920s and 1930s, American Oil Company continued to market its premium-grade gasoline – Amoco – as a lead-free fuel utilizing aromatics as an octane booster (American’s regular gas however was a leaded fuel as it was not as economical to sell the high-volume low-priced gasoline as a lead-free due to high production costs). Amoco was sold in several eastern and southern states since the 1910s. The lead free gasoline was marketed as simply Amoco or Amoco-Gas until 1961 when it was renamed American Super-Premium, and had reached a Research octane of 100 – similar to competitor’s leaded premium fuels – but sold about 1 to 2 cents higher per gallon.

I would like to see or hear former muscle car owners back in the day who predominately used Amoco’s lead-free premium when those cars were new – and how well their vehicles held up in the face of reports that pre-1971 engines could suffer valve recession and other damage from predominant use of such fuel that continue to this day. I have heard of reports from owners of 50s and 60s cars with high-compression engines that used Amoco Super-Premium almost exclusively including Buicks, Cadillacs and Chryslers, stating that spark plugs were cleaner and lasted longer, and exhaust systems lasted much longer due to absence of corrosion caused by use of leaded gasoline.

Actually the premium-grade lead-free gasoline marketed by the American Oil Company was called Amoco Super-Premium, not American Super-Premium as I implied – The lead-free Amoco product was marketed by the firm only in the eastern and southern U.S. while the rest of American’s marketing area throughout the nation (including its Standard Oil territory in the Midwestern U.S.) the premium-grade gasoline was called American Super-Premium, but that fuel was of the leaded variety as was American’s regular gas.

Amoco’s lead-free premium would not spread to its Standard Oil territory until 1977, when it was it was rolled out to replace the leaded American high-octane juice – first to the larger markets including Chicago, Detroit, Milwaukee, Indianapolis, St. Louis, Denver, Kansas City and Minneapolis-St. Paul, and then the rest of the region.

That fuel is still being marketed today by Amoco/Standard successor BP as Amoco Ultimate.

>For the 1971 model year, the only GM engine requiring high-octane, leaded fuel was the high-strung LT-1 in the Corvette and Camaro. Even its compression ratio dropped from 11.0:1 to 9.0:1 — just a little too high for most available regular-grade fuels, leaded or not.<
Sorry, but that statement is incorrect. All 1971 Chevrolet (and other GM divisions) engines were designed to run on regular, low-lead or no-lead gasoline with a Research Octane of 91 or higher - that was a Corporate mandate from the 14th Floor to all divisions. All engines from the four-cylinder Vega to the 330-horsepower LT-1 350 in Camaro Z-28 and Corvette and the 425-horsepower LS-454 offered in the Corvette.
All of the car brochures from each of the GM divisions for 1971 included the above engine disclaimer of regular, low-lead or unleaded gasoline in the engine specification/availability charts, along with ALL of the owner's manuals that came in the gloveboxes of GM cars and trucks.
There was NOT a single engine in GM's lineup for 1971 that required high-octane premium gasoline due to the corporate mandate requiring engines to use the lower-octane gasolines.
Ford Motor Company and Chrysler Corporation did continue to offer some high-compression premium fuel engines for one last time in 1971.
Ford's high-compression engines included the 351 Cleveland 4-V, the Boss 351 Mustang engine, as well as all 429 and 460 cubic-inch V8s.
Chrysler's premium fuel engines for 1971 included the 340 Magnum offered in the compacts and ponycars, and the top musclecar engines for the Road Runner, GTX, Charger R/T and Super Bee incuding the 440 Magnum, 440 Six-Pack and the 426 Hemi.
American Motors offered only one single premium fuel engine for '71 - the 330-horsepower 401 V8 offered in the Javelin, Matador and Ambassador.
Ford and AMC discontinued premium fuel engines entirely for the 1972 model year, while Chrysler barely slipped by with the 440 Six-Pack available in the Plymouth Road Runner and Dodge Charger, but only 12 cars were built with this engine - all of them very early in the model year in August and September, 1971. Sure this engine was listed in the '72 brochures but was quickly discontinued shortly after the start of the year because it couldn't meet the Federal emission regulations - and completely blackballed in California.
For most of the '72 model year, Chrysler's hottest engines were the 240-horsepower 340 Magnum and the 280-horsepower 440 Magnum, both low-compression regular-fuel powerplants.

"By the 1950s, some scientists had begun to link the deleterious effects of high levels of lead contamination, both from the used of leaded paint and the widespread use of leaded gasoline, to a sobering array of health problems, particularly among children, including low IQ, mental retardation, and learning disabilities. By the early 1970s, some U.S. public health officials characterized it a public menace."

"By the late 1960s, there was a renewed movement to eliminate the use of lead in gasoline. In 1969, U.S. Secretary of Health, Education, and Welfare (HEW) Robert Finch proposed that the major oil companies begin phasing out leaded gasoline, starting in the summer of 1971. To the shock of nearly everyone in the industry, GM president Ed Cole made a similar proposal at a Society of Automotive Engineers talk in January 1970."

What I find an open question for debate is what factors contributed to the strong push for environmental and public health regulations of automobile emissions in the planning euphoria from the late ’60s until the early ’70s. Scientific knowledge of dangers of leaded gasoline seem to have grown for two decades before serious moves were made to regulate lead out of gasoline, just as did concern over smog had existed since after WWII before the federal government started making strong moves to cut gaseous emissions.

In addition to thinking about social factors that might have pressured politicians to regulate the auto industry on pollution, it is also important to think about how the government’s regulatory efforts played out through the 1970s with shifting public and industry support. This is a fantastic look at the history of the removal of leaded gasoline in America, and I wonder what your thoughts are on the reasons why environmental regulation moved at different speeds through the 1960s, ’70s, and early 1980s. There are certainly many interesting stories to be told from these regulatory dramas.

Not professing to be a fuel expert, but it was interesting while I was working over in Saudi Arabia that all of their gas stations (and I do mean all) had the same two fuel options of 91 and 95, whereas back in North America, fuel gets down to 87. I’m not sure if they were all lying or not, but it makes you wonder how they got that higher octane.

Several things here. First of all, there’s no particular reason (other than cost) you can’t get unleaded fuel with more than 92-93 pump octane. Less than two miles from me, for example, is a gas station that sells 100 octane unleaded racing fuel — it’s expensive, but it’s legal and it’s available to anyone with the money to spend. I assume the reason 92-93 is the common upper end for pump gasoline is a trade-off of cost and demand, since most modern cars don’t need more than that. If another market favored higher compression ratios and didn’t commonly have knock sensors, it might be a different story.

The other consideration is that the fuel stations in Saudi Arabia may not be advertising octane on the same scale used here. In the U.S., retailers are currently required to display the octane rating of their gasolines in "pump octane," which is the average of two different methods for measuring fuel octane: the research method and the motor octane method. In other parts of the world, it’s not uncommon to advertise fuel using only one or the other, more commonly the research octane number (RON). Because pump octane is an average, there is no way to know its research octane rating unless the company chooses to release either the motor octane or research octane ratings for their particular gasoline. However, the RON is usually higher than the pump octane rating, so 91 RON would probably give you something in the vicinity of 85 pump octane, while 95 RON would probably give you about 88-89 pump octane.

My (admittedly unresearched) guess is that Saudi Arabian gas falls into the latter category, and you have cheap fuel that is actually somewhat lower octane than U.S. regular unleaded and a more expensive premium that falls somewhere between U.S. regular and mid-grade fuels.

Great article with great research. I am glad that the public health concerns were also included. The lead controversy was also taken up by the Mayo Clinic and the Surgeon General of the time. They predicted the population most to be affected by aspirated lead compounds would be low income families and industrial workers; owing to their work areas and low value properties in and around thoroughfares and industrial areas. Lead wasn’t the total answer initially. Ford had put some engineering/service bulletins detailing exhaust valve corrosion from lead fuel additives. Bromine, the ethylene dibromide, came on the scene as a scavenging agent to expel it with the engine’s exhaust. International Harvester had published service bulletins about lead fouling on engine valves and spark plugs during sustained high speed high load engine operation. Their answer was to switch to a lead-free fuel with the suitable octane requirement. I believe this IH bulletin, somewhere in my library, is an early 60’s vintage. The public health predictions unfortunately rang true. I’m a motor-head my self, but I also enjoy life for myself and others. I’m damn glad they got the lead out!

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